Antideuteron based dark matter search with GAPS: Current progress and future prospects

The General Antiparticle Spectrometer (GAPS) is a new approach to the indirect detection of dark matter. It relies on searching for primary antideuterons produced in the annihilation of dark matter in the galactic halo. Low energy antideuterons produced through Standard Model processes, such as collisions of cosmic-rays with interstellar baryons, are greatly suppressed compared to primary antideuterons. Thus a low energy antideuteron search provides a clean signature of dark matter. In GAPS antiparticles are slowed down and captured in target atoms. The resultant exotic atom deexcites with the emission of X-rays and annihilation pions, protons and other particles. A tracking geometry allows for the detection of the X-rays and particles, providing a unique signature to identify the mass of the antiparticle. A prototype detector was successfully tested at the KEK accelerator in 2005, and a prototype GAPS balloon flight is scheduled for 2011. This will be followed by a full scale experiment on a long duration balloon from Antarctica in 2014. We discuss the status and future plans for GAPS.     

Putative graviperception mechanisms of protists.

Many (if not all) free-living cells use the gravity vector for their spatial orientation (gravitaxis). Additional responses may include gravikinesis as well as changes in morphological and physiological parameters. Though using essentially different modes of locomotion, ameboid and ciliated cells seem to rely on common fundamental graviperception mechanisms. Uniquely in the ciliate family Loxodidae a specialized intracellular gravireceptor organelle has been developed, whereas in all other cells common cell structures seem to be responsible for gravisensing. Changes in direction or magnitude of acceleration (from 0 to 5 g) as well as experiments in density-adjusted media strongly indicate that either the whole cytoplasm or dense organelles like nuclei act as statoliths and open directly or via cytoskeletal elements mechano-sensitive ion channels in the cell membrane. A recent spaceflight experiment (S/MM-06) demonstrated that prolonged (9 d) actual weightlessness did not affect the ability of Loxodes to respond to acceleration stimuli. However, prolonged cooling (> or = l4 d, 4-10 degrees C) destroyed the ability for gravitactic orientation of Paramecium. This may reflect a profound effect either on the gravireceptor itself or on the gravity-signal processing. In gravity signalling the ubiquitous second messenger cAMP may be involved in acceleration-stimulus transduction.     

The IMF pile-up regions near the Earth and Venus: lessons for the solar wind - Mars interaction

The Mars Global Surveyor mission has revealed that localized crustal paleomagnetic anomalies are a common feature of the Southern Hemisphere of Mars. The magnetometer measured small-scale magnetic fields associated with many individual magnetic anomalies have magnitudes ranging from hundreds to thousands nT at altitude above 120 km. That makes Mars globally different from both Venus and Earth. The data collected by Lunar Prospector near the Moon were interpreted as evidence that above regions of inferred strong surface magnetic fields on the Moon the SW flow is deflected, and a small-scale mini-magnetosphere exists under some circumstances. With a factor of 100 stronger magnetic fields at Mars and a lower SW dynamic pressure, those conditions offer the opportunity for a larger size of small `magnetospheres' which can be formed by the crustal magnetic fields. Outside the regions of the magnetic anomalies, the SW/Mars interaction is Venus-like. Thus, at Mars the distinguishing feature of the magnetic field pile-up boundary most likely varies from Venus-like to Earth-like above the crustal magnetic field regions. The observational data regarding the IMF pile-up regions near Venus and the Earth are initially reviewed. As long as the SW/Mars interaction remains like that at Venus, the IMF penetrates deep into the Martian ionosphere under the `overpressure' conditions. Results of numerical simulations and theoretical expectations regarding the temporal evolution of the IMF inside the Venus ionosphere and appearance of superthermal electrons are also reviewed and assessed.     

Microperturbations on the <Emphasis Type="Italic">International Space Station</Emphasis> during physical exercises of the crew

The results of a preliminary analysis of microperturbations on the International Space Station during physical exercises of the crew are presented. The goal of this paper is to identify the parameters of perturbations when physical exercises are performed. The results of measurements by sensors of microaccelerations of both Russian and American segments during physical exercises in the service module of the Russian segment are analyzed.     

Revisiting Perspective-Taking: Can People Maintain Imagined Perspectives?

Abstract

Three experiments were conducted to examine whether people can adopt and maintain imagined perspectives in the absence of target information. The task used entailed providing information about an imagined perspective in advance of target information to examine whether this would facilitate perspective-taking performance and reduce or eliminate alignment effects that are commonly reported in the literature. The three experiments employed different types of spatial environments: an environment learned from navigating a computer screen (Experiment 1), and an immersive environment that was either remote (Experiment 2) or immediate (Experiment 3) at the time of retrieval. Across the three experiments, results showed that information about an imagined perspective can be utilized ahead of target information. Furthermore, they suggested that alignment effects can be reduced as a result of processing information about perspective ahead of target information, but only when reasoning about specific nonimmediate spatial relations (Experiments 1 and 2). Results are discussed in connection with previous findings on spatial updating and the organizational structure of spatial memory.     

Optical properties of the undisturbed mesosphere from wide-angle twilight sky polarimetry

The paper describes the first results of all-sky polarization measurements of the twilight background started in central Russia in the very beginning of summer 2011. Time-frequency data of the sky intensity and polarization over a wide range of sky point zenith distances are used to separate single and multiple scattering and construct the altitude dependence of the scattering coefficient and polarization in the mesosphere (altitudes from 60 to 90 km) at different angles. The undisturbed structure of the mesosphere without noticeable aerosol stratification on observation days makes it possible to estimate the temperature of the atmosphere at these altitudes.     

Studies of Comets in the Ultraviolet: The Past and the Future

The remote sensing of comets in the ultraviolet bandpass has been a valuable tool for studying the structure, composition, variability, and physical processes at work in cometary comae. By extension, these studies of comae have revealed key insights into the composition of cometary nuclei. Here we briefly review the ultraviolet studies of comets, and then take a look toward the future of such work as anticipated by the advent of several key new instruments. This revised version was published online in June 2006 with corrections to the Cover Date.     

A method to ensure energy security of satellite communication systems

A method is substantiated to ensure energy security for the satellite communication systems (SCS) at a close position of the radio interception receiver. This is done by lowering the carrier frequency down to f ₀ = 60…80 MHz and by applying spaced measurements with n ≥ 4 receiving antennas.     

Stellar coronagraph using the principle of achromatic null-interferometer

In order to observe exoplanets we propose a space-based achromatic stellar coronagraph combined with a 0.8–1.5 m telescope. We develop an achromatic common path interferometer for observing an exoplanet (a faint off-axis source) on the background of a hoste star (bright axial source). An image of the star and its copy acquire an achromatic phase shift by 180° and interfere in antiphase. The achromatic phase shift is caused by geometric phase in the scheme of a three-dimensional interferometer. The interference process divides spatially the dark and light fields of the star image redirecting them to the opposite sides of a beam splitter. The interference process does not weaken the image of a planet, with equal intensities it is redirected to both sides of a beam splitter. The suggested scheme of common path interferometer ensures mechanical stability. The background signal is experimentally demonstrated to be reduced by six orders of magnitude.     

Analytic expansions of luni-solar gravity perturbations along rotating axes for trajectory optimization—Part 2: The multipliers system and simulations

An efficient self-contained trajectory optimization software is generated by making use of de Pontécoulant's analytic lunar theory removing the need for an outside third body ephemeris program to compute the lunar and solar position vectors at each integration step. The accelerations being further resolved along the rotating Euler–Hill frame after expansion to third order in the spacecraft radial distance, the adjoint differential equations are derived in a direct manner complementing the generation of the dynamic system of equations for full compatibility. Because the variation of parameters equations are cast in terms of the nonsingular equinoctial elements with the perturbation accelerations resolved in their analytic form along the rotating axes, the adjoint equations are also derived in the same manner providing a highly efficient and accurate system of equations for rapid computations in conjunction with Aerospace Corporation's NLP2 nonlinear programming codes to search for the initial values of the multipliers that steer the spacecraft towards its target orbit in minimum time. Numerical simulations show that the solutions obtained by the analysis developed in this paper are essentially identical to the more indirect approach based on the use of inertial accelerations obtained from a separate ephemeris generator and subsequent conversions to the thrust frame and equinoctial system.